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Marvin is a free UCI/XBoard compatible chess engine. It does not provide it's own user interface, instead is is intended to be used with an UCI or XBoard compatible GUI, such as XBoard/WinBoard, Arena, HIARCS Chess Explorer, Shredder or Fritz. For instructions on how to install the engine see the documentation for the respective GUI.


Marvin was originally released as closed source in 2002 and activly developed until 2005. The last release was 1.3.0. In 2015 the development was restarted and a completely rewritten version was released as open source in 2017.


When started Marvin looks for a configuration file called marvin.ini in the same directory as the excutable. This file can be used to configure the engine. The settings in the configuration file acts as default values for UCI options. Currently the following options are recognized:

  • HASH_SIZE: The amount of memory used for the main hash table (in MB). For best performance the size should be a power-of-2.
  • LOG_LEVEL: The log level. If set to 2 the engine will log all commands that are sent and received.
  • SYZYGY_PATH: Path to where the Syzygy tablebases are located.
  • NUM_THREADS: The number of threads to use for searching.

Additionally Marvin looks for a file called book.bin in the same directory as the executable. The book.bin file should be an opening book file in Polyglot format.


Pre-built binaries for Windows and Linux are included with each release. A few different builds are provided for each platform. On most computers the -avx2 build will be the fastest followed by -modern. However it may not work on all computers. The -modern build should work on all computers except very old ones.

To compare the builds run Marvin in a terminal (or double-click on the exe-file in Windows) and run the 'bench' command. This will run a single-threaded benchmark and print out some statistics. The benchmark can also be run by starting Marvin with the '-b' option.


Starting from version 5.0.0 Marvin uses a neural network for evaluation. A network file is included in the binaries package and should be put in the same folder as the engine executable. Network files can also be downloaded here.


The easiest way to build Marvin is to use the included Makefile and just run make. This should produce a binary that is compatible with most systems. The default compiler is Clang, but if you want to use GCC instead run make CC=gcc. However if you plan on using NNUE I highly recommend using Clang since a GCC build will be almost 100 ELO weaker. For more information about available targets and build options run make help.


The source code is provided under the GPLv3 license. For details see the LICENSE file.

Marvin uses the Fathom library ( for probing Syzygy tablebases. The Fathom library is licensed under the MIT license. For details see the LICENSE file in the import/fathom folder.